A spin coating method has conventionally been known as a method of coating a coating liquid on a substrate such as, for example, a semiconductor wafer or a glass substrate. The spin coating method is a method of diffusing a coating liquid dropped on a substrate by a centrifugal force to be spread on the substrate. However, the spin coating method is not desirable in terms of use efficiency of the coating liquid because most of the dropped coating liquid is scattered to the outside of the substrate.
Accordingly, a slit coating method has been proposed as a coating method in place of the spin coating method. The slit coating method is a method of applying a coating liquid on a substrate by scanning an elongated slit nozzle having a slit-shaped ejecting port.
For example, a substrate is horizontally placed on a stage, and a coating liquid slightly exposed from the ejecting port of the slit nozzle comes in contact with the substrate. In this state, the slit nozzle is horizontally moved and the coating liquid is drawn out to form a coating film on the substrate (see, e.g., Japanese Patent Laid-Open Publication No. 2008-68224). According to the slit coating method, since the slit nozzle is moved only once from one end of the substrate to the other end, a coating film may be formed on the substrate without dropping the coating liquid outside the substrate.
Here, the slit nozzle disclosed in Japanese Patent Laid-Open Publication No. 2008-68224 is provided with a liquid trapping portion to store the coating liquid, and the coating liquid stored in the liquid trapping portion is ejected from a slit-shaped ejecting port through a slit-shaped path.